1. Field of the Invention
The present invention relates to a capacitor device, an electronic parts packaging structure, and a method of manufacturing the capacitor device and, more particularly, a capacitor device capable of being applied to a decoupling capacitor that is arranged on a circuit substrate on which high-speed operated electronic parts are mounted to stabilize a power supply voltage and also reduce a high-frequency noise, an electronic parts packaging structure in which such capacitor device is built, and a method of manufacturing the capacitor device.
2. Description of the Related Art
In recent years, reduction in the power-supply voltage due to increase in a processing speed and reduction in power consumption is accelerated in the digital LSIs including the microprocessor. In such digital LSIs, a power-supply voltage of the LSI is apt to become unstable when the impedance of the LSI is suddenly varied, and so forth. Also, a stable operation in a higher-frequency (GHz) range is required of high-speed operated digital LSIS, and thus it is needed to prevent the malfunction of the LSI due to the high-frequency noise.
Therefore, for the purpose of stabilizing the power-supply voltage and reducing the high-frequency noise, the decoupling capacitor is arranged between a power-supply line and a ground line of the LSI.
For instance, in Patent Literature 1 (Patent Application Publication (KOKAI) 2001-110675) and Patent Literature 2 (Patent Application Publication (KOKAI) 2002-260960), as the capacitor incorporated into the printed wiring substrate, the capacitor utilizing the metal oxide film obtained by applying the anodic oxidation to the valve metal such as tantalum, or the like as the dielectric layer is set forth.
In the circuit substrate having the conventional decoupling capacitor, such capacitor is packaged onto the area of the circuit substrate adjacent to the area on which the LSI chip is packaged. In this case, since leads must be provided between the LSI chip and the capacitor, a relatively large inductance is present between these leads. Therefore, even though the decoupling capacitor is provided, an effect of suppressing a variation in the power-supply voltage applied to the high-speed operated electronic parts and also reducing the high-frequency noise is lessened.
As a result, the method of setting the wiring distance between the LSI chip and the capacitor to the shortest length by placing the decoupling capacitor directly under the LSI chip to reduce the inductance is proposed.
However, there is a limit to the reduction in the parasitic inductance even though the wiring distance between the LSI chip and the capacitor is set to the shortest length. Then, when the higher frequency of the LSI is further forwarded, such a situation is supposed that either the power-supply voltage of the LSI becomes unstable or the malfunction of the LSI is caused by the high-frequency noise. As a result, the decoupling capacitor having the characteristic that its impedance is reduced over a wider frequency band is requested.